Biology · Biomolecules · NEET
One glycerol and three fatty acids. Glycerol has only THREE –OH (hydroxyl) sites, so it can hold at most three fatty acids. This is why a typical fat is called a triglyceride (tri = three). The reverse, three glycerol and one fatty acid, is impossible. NEET picks this exact trap (NEET 2016).
There is NO difference in the type of molecule. NCERT says fats and oils are named only by their melting point. Oils have a LOWER melting point (example: gingelly oil), so they stay liquid at room temperature and even in winter. Fats have a higher melting point, so they stay solid. Both are glycerides.
Glycerol can join with 1, 2, or 3 fatty acids. One fatty acid + glycerol = monoglyceride. Two = diglyceride. Three = triglyceride. A typical body fat is a triglyceride.
Yes. Both fats and oils are esters of glycerol with fatty acids, so both are glycerides. Do not think oils are a separate class. The only sorting is by melting point.
NCERT (Class 11) only requires the melting-point rule for NEET: oils have a lower melting point, so they remain liquid; fats have a higher melting point, so they stay solid. The deeper reason (unsaturated fatty acids with C=C bonds lower the melting point) links to the saturated vs unsaturated fatty acids topic.
Glycerol is trihydroxy propane. It is a 3-carbon molecule with three –OH groups. Those three –OH groups are the reason one glycerol can bind three fatty acids to form a triglyceride. NEET has asked directly: 'Trihydroxy propane is glycerol' (a true statement).
A typical fat molecule is made up of:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A glyceride is a lipid formed when glycerol joins with one or more fatty acids by ester bonds. When three fatty acids join one glycerol, it is a triglyceride, the common storage fat in the body.
Yes. For NEET (NCERT Class 11), oils are just fats with a lower melting point. Both are glycerides. Do not treat them as chemically different classes.
An ester bond (also called an ester linkage). Each –OH of glycerol reacts with the –COOH of a fatty acid to form an ester bond, releasing water.
No. Lipids, including fats and oils, are NOT polymers. They are esters, not chains of repeating monomers. NEET 2017 asked which biomolecule is 'not polymeric' and the answer was lipids.
Gingelly (sesame) oil is NCERT's example of an oil with a low melting point that stays liquid even in winter. It shows that oils and fats differ only by melting point.
